The ultimate objective of this research is to develop an alternative approach to the contemporary chemical means of insect pest control. This alternative involves the utilization of neurohormones as means of biological control, but its development can be realized only when basic information is available on the endocrinology of a major insect peptide neurohormone, prothoracicotropic hormone (PTTH), which is responsible for the initiation of postembryonic development and metamorphosis in insects. Because of the paucity of background information about PTTH, this research has been initially directed toward elucidating the endocrinology of this neurohormone. The experimental objectives entail: 1) the elucidation of the chemical nature and structure of PTTH; 2) the generation of an antibody to PTTH, and with it, the development of a radioimmunological assay; 3) the cellular localization of the site of synthesis and release of PTTH; 4) a titer of PTTH in the brain and hemolymph; and 5) the development of an in vitro culture system for the synthesis of PTTH.